Reduce number of branches

[GegznaV]

It seems that the current repo has many branches, e.g.:

I'm confused especially about the develop, devel_2017 and master branches. Can you please comment on why they are needed?

I Suggest merging and deleting as many branches as possible. @rguliev, can you take care of that?

Then it would be reasonable to flatten the R package structure (#33), and then fix GHA workflows (#38) and other automatic tools we use to maintain r-hyperspec. Then we may apply automatic tools to improve code quality and unify code style.